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CVE-2021-39185 Http4s

Affected softwareHttp4s
Severity9.1 Critical CVSS 3.1 2 scores
Fixed in0.22.3, 0.23.2
WeaknessCWE-346
Published1 Sep 2021
Updated17 Jun 2026

Description

Http4s is a minimal, idiomatic Scala interface for HTTP services. In http4s versions 0.21.26 and prior, 0.22.0 through 0.22.2, 0.23.0, 0.23.1, and 1.0.0-M1 through 1.0.0-M24, the default CORS configuration is vulnerable to an origin reflection attack. The middleware is also susceptible to a Null Origin Attack. The problem is fixed in 0.21.27, 0.22.3, 0.23.2, and 1.0.0-M25. The original CORS implementation and CORSConfig are deprecated. See the GitHub GHSA for more information, including code examples and workarounds.

Exploitation status

No public exploit

No exploit has been reported in the sources we check. Published 5 years ago.

  • CISA KEV not listed
  • VulnCheck KEV not listed
  • CISA Vulnrichment no assessment published
  • Indexed PoC none indexed
  • EPSS 0.59% chance in 30 days

Waratek protection

No exploit published

Within Waratek scope. In the sources we check, nobody has published exploit code for this CVE or reported it being exploited.

A public code fix exists.

  • Protection none
  • Action unverified
  • Review automated Upstream data
  • Record active
Decided by Exploit code for this candidate, published in a reviewed catalogue or a GitHub repository with 5 or more stars, or in use per CISA or VulnCheck; not only a CISA verdict, a forecast, or nothing at all
Finding This CVE is not listed in CISA KEV or VulnCheck KEV, CISA Vulnrichment records no active exploitation, no reviewed exploit catalogue carries an entry for it, and no GitHub PoC repository for it has 5 or more stars. Nobody has published exploit code worth tracing, so it is not a candidate for a rule ahead of the ones where somebody has; an upstream fix path does exist, so the remediation half of the candidacy still holds. This is a statement about what has been published, not about whether the defect is reachable or serious.
Candidate fix https://github.com/http4s/http4s/security/advisories/GHSA-52cf-226f-rhr6 : the maintainers' own security advisory: names the version that fixes it, so the fix is the difference between two releases

CVSS

9.1 CRITICAL v3.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N 2 metrics

We show the highest score from the newest CVSS version. Scores from different versions can't be compared, and the first score listed is sometimes a 0.0 placeholder.

VersionScoreBandVectorAssignerType
CVSS 3.1 9.1 CRITICAL CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N security-advisories@github.com Secondary published
CVSS 2.0 6.4 none AV:N/AC:L/Au:N/C:P/I:P/A:N NVD Primary

Affected software and releases

Maven packages

Affected and fixed versions, from OSV.dev
PackageIntroducedFixedLast affected
org.http4s:http4s-server_2.13.0-M5 0 none unbounded
org.http4s:http4s-server_3 0.22.0 0.22.3 unbounded
org.http4s:http4s-server_3 0.23.0 0.23.2 unbounded
org.http4s:http4s-server_2.10 0 none unbounded
org.http4s:http4s-server_2.11 0 none unbounded
org.http4s:http4s-server_2.12 0 0.21.27 unbounded
org.http4s:http4s-server_2.12 0.22.0 0.22.3 unbounded
org.http4s:http4s-server_2.12 0.23.0 0.23.2 unbounded
org.http4s:http4s-server_2.13 0 0.21.27 unbounded
org.http4s:http4s-server_2.13 0.22.0 0.22.3 unbounded
org.http4s:http4s-server_2.13 0.23.0 0.23.2 unbounded

Products and versions

7 products, 39 version entries
SourceVendorProductSchemeAffected versions
osv org.http4s http4s-server_2.10 generic any version
osv org.http4s http4s-server_2.11 generic any version
osv org.http4s http4s-server_2.12 generic < 0.21.27 · ≥ 0.22.0 and < 0.22.3 · ≥ 0.23.0 and < 0.23.2
osv org.http4s http4s-server_2.13 generic < 0.21.27 · ≥ 0.22.0 and < 0.22.3 · ≥ 0.23.0 and < 0.23.2
osv org.http4s http4s-server_2.13.0-M5 generic any version
osv org.http4s http4s-server_3 generic ≥ 0.22.0 and < 0.22.3 · ≥ 0.23.0 and < 0.23.2
nvd typelevel http4s generic ≤ 0.21.26 · ≥ 0.22.0 and ≤ 0.22.2 · 0.23.0 · 0.23.1 · 1.0.0:milestone1 · 1.0.0:milestone10 · 1.0.0:milestone11 · 1.0.0:milestone12 · 1.0.0:milestone13 · 1.0.0:milestone14 · 1.0.0:milestone15 · 1.0.0:milestone16 · 1.0.0:milestone17 · 1.0.0:milestone18 · 1.0.0:milestone19 · 1.0.0:milestone2 · 1.0.0:milestone20 · 1.0.0:milestone21 · 1.0.0:milestone22 · 1.0.0:milestone23 · 1.0.0:milestone24 · 1.0.0:milestone3 · 1.0.0:milestone4 · 1.0.0:milestone5 · 1.0.0:milestone6 · 1.0.0:milestone7 · 1.0.0:milestone8 · 1.0.0:milestone9

References

URLTags
https://github.com/http4s/http4s/security/advisories/GHSA-52cf-226f-rhr6 advisory
https://github.com/http4s/http4s PACKAGE
https://github.com/http4s/http4s/releases/tag/v0.23.2 WEB

Timeline

Published2021-09-01By the CVE Program.
NVD record modified2026-06-17NVD's own last-modified date for this record.